he definition, content and evaluation standards of red soil nutrient degradation are proposed. Research results showed that about 80% of the soil area in hilly region belongs to severe and extremely severe degradation class for soil phosphorous, and 20% for N, 10% for potassium. Leaching is the main mechanism for N degradation in soil, especially because the nitrification process is rapid in this region. For P, the fixation process is considered to be the main cause for P degradation. The amount of P fixe...